1. Technical Field
The present invention relates to a printer having an inverting conveyance path that inverts the front and back sides of recording paper or other sheet media while the media is conveyed, and to a control method of the printer.
The present application claims priority based on and incorporates by reference the entire contents of Japan Patent Application No. 2013-140425 filed in Japan on Jul. 4, 2013, and Japan Patent Application No. 2013-140428 filed on Jul. 4, 2013.
2. Related Art
Printers with an automatic duplex (two-sided) print function are one example of a printer with a inverting conveyance path. In a printer with an automatic duplex print function, the recording paper is printed on one (front) side, the front and back of the recording paper are then reversed by conveyance through the inverting conveyance path, and the other (back, second) side of the recording paper is then printed. JP-A-2007-38562 discloses a printer with an inverting conveyance path.
Problems can occur when the recording paper is conveyed to the inverting conveyance path and reversed after printing the front. These problems include a drop in print quality as a result of ink that has not dried yet sticking to the conveyance mechanism, and paper jams resulting from changes in the paper caused by the ink. The printer disclosed in JP-A-2007-38562 applies control to prevent the occurrence of such problems. More specifically, after printing on the front, the recording paper is reversed at slow speed until the trailing end of the recording paper is just before the paper feed roller pair, the recording paper then pauses at this position until the ink is completely dry, and back-feeding then resumes to feed the recording paper into the inverting conveyance path and reverse the recording paper.
The printer taught in JP-A-2007-38562 dries the ink after the trailing end of the recording paper is returned to immediately before the paper feed roller pair. The success rate of the recording paper nipping operation of the paper feed roller pair is therefore high, and the chance of paper jams occurring during the inverting operation is low. Furthermore, because the inverting operation occurs after waiting for the ink to dry completely, ink bleeds and ink sticking to the paper feed rollers is prevented. A drop in print quality can also be prevented.
The media inverting conveyance control method of the printer disclosed in JP-A-2007-38562 requires a long time for the inverting operation, however, because media is conveyed at low speed in reverse and there is a wait period imposed for the ink to dry in front of the paper feed roller pair. Throughput therefore drops during duplex printing. Setting the desirable length of the wait period for drying the ink is also difficult because the appropriate wait time varies according to the type of recording paper. The wait period must also be set to the longest possible drying time when printing on multiple different types of paper is possible in order to reliably dry the ink on all types of paper. The time required for the inverting operation may therefore become unnecessarily long. Paper jams can also occur in inkjet printers because of ink-induced changes in the paper before the recording paper is fed into the inverting conveyance path, but the literature is silent about a means of avoiding such problems, and a means of suppressing a drop in throughput.
In addition, when the recording paper is reversed after printing and fed into the inverting conveyance path, the condition of the trailing end of the recording paper before reverse conveyance starts differs according to the content printed on the front printing surface and the printing method. For example, when the recording paper is printed nearly to the trailing end, the trailing end of the recording paper may have left the nipping point of the paper feed roller pair before reverse conveyance starts. Because the paper feed roller pair may fail to nip the recording paper during reverse conveyance when this happens, paper jams can occur if nipping failures cannot be avoided, and throughput will drop. The position of the trailing end of the media when printing is completed differs according to how the last printing pass was printed when printing on the front side, and this affects throughput.
Printing on the front side may also end while the trailing end of the recording paper is in the paper conveyance path on the upstream side of the junction to the inverting conveyance path. If inverting the recording paper is started from this position after printing the front ends, the recording paper will be fed to the paper cassette side, and cannot be fed into the inverting conveyance path. Therefore, the recording paper must be conveyed in the same direction as the printing direction until the trailing end of the recording paper is on the downstream side of the junction before reverse conveyance can start. However, this forward conveyance is meaningless and lowers throughput unnecessarily when the trailing end of the recording paper has already escaped from the nipping point of the paper feed path.
When feeding the recording paper in reverse to the inverting conveyance path after printing on the front printing surface of the medium in a printer that can print automatically on both sides of media, optimal conveyance control differs according to the state of the trailing end of the recording paper when reverse conveyance starts, and throughput may drop unnecessarily if conveyance control is the same at all times. The control method taught in JP-A-2007-38562 does not address this problem.